FR 2 896 935, dated 27 Jun. 2006, describes an approach for overcoming the problems of the so-called “bell-wire” when home extension telephone wiring which includes such a bell wire is used for carrying DSL signals. The bell wire is a third wire which is connected to the two incoming copper conductors (the “drop wire”) via a filter in such a way that a ringing signal transmitted over the incoming “drop wire” will be passed onto the bell wire and will thus cause the bell of a suitably connected telephone to ring, while other signals (e.g. associated with pulse dialling performed by another telephone within the same home wiring system) will not be carried onto the bell wire. The bell wire is therefore used to overcome the problem of tinkling which sometimes otherwise occurred in conventional analog telephone systems. However, as noted in FR 2 896 935, this bell wire caused problems with DSL systems (when they were introduced) as the bell wire appears to a DSL modem as a bridged tap at DSL frequencies and also tended to pick up noise which also caused problems for the DSL signals. To mitigate these problems, FR 2 896 935 proposes connecting another pair of wires (which includes the bell wire as one of the pair of wires) with the signal carrying wires within the home extension wiring to provide an additional parallel pair of wires for carrying signals on over the home wiring. For example, in France, the drop wire conductors A and B are typically connected to the 1 and 3 wires within a 6-wire home extension wiring system and the 5 wire acts as the bell wire; with such a configuration, FR 2 896 935 proposes connecting wire 1 directly to wire 5 and wire 3 to wire 2. This effectively shortcuts the filter between the A wire and the bell wire. Additionally, at each point where a device connects to a home wiring extension socket a dongle is used which also connects together the 1 and 5 wires and the 2 and 3 wires. Thus all signals are now carried over two pairs of wires through the extension wiring with no filtering between any of them. This greatly improves performance in the presence of a functioning bell wire and does not hinder performance in cases where the bell wire had been disconnected (or never connected).
More recently, attention in the industry has turned towards high speed DSL systems such as VDSL systems which require the DSL connection (i.e. the part of the connection over copper cables) to be as short as possible in order to provide the fastest connections. It has therefore been proposed to place DSL modems, at the network side (network modems), at so called “drop points”. Such drop points might typically, for example, be at the top of a telegraph pole from where a number of telephone lines fan out each heading towards a different house. Such a point is likely to be the final distribution point before the external cable reaches the customer's premises.
In such situations it can be difficult for the network modem at the distribution point to obtain a reliable power supply from its immediate vicinity. Solutions have therefore been devised by which power is supplied from the consumer's premises over the copper pair connection together with the DSL signals.
In such scenarios normal telephony is normally provided by a Voice Over Internet Protocol (VOIP) solution because otherwise the reverse power (e.g. as a 50 volt d.c. supply) would appear as a signal which would disrupt normal conventional analog telephony signals. Generally, to provide this VOIP solution, the DSL modem in the customer's premises is configured to provide a socket into which a conventional lead, having a conventional plug (e.g. a Registered Jack (RJ) 11 or 45 or a conventional BT plug, etc.) from a conventional telephone apparatus may be plugged. The modem simulates all of the Plain Old Telephone System (POTS) functionality (including various DC and other low frequency signals) generally provided by a conventional master socket which provides the interface between the customer's premises and the access network such that the telephone (for example an analog telephone) can operate normally as though it were directly connected to the master socket (e.g. a conventional British Telecommunications (BT) Network Termination Equipment (NTE) 5 model) or an extension socket correctly connected to the master socket.
However, when a telephone is connected directly to the user modem in this way, it becomes difficult for a user to use any existing extension telephone wiring (e.g. to extension sockets) for connecting additional telephones in locations which may be considerably removed from the user's modem.
FR 2 933 835 describes an approach for solving this problem in which an alternative pair of wires to those normally used for carrying telephony signals are used for carrying the VOIP signals. In order to do this, various dongles are installed which provide sockets into which the telephones to be connected are plugged—one of these dongles includes a port into which the modem is to be connected and connects to the conducters within the extension wiring which are connected at the termination unit to the incoming drop wires. The dongles connect the normally used wires (wires 1 and 3) from the telephone leads to an alternative pair of wires in the user's existing extension wiring (e.g. wires 4 and 5 although they expressly point out that any pair of unused wires could be used—e.g. any pair from the 2, 4, 5 and 6 wires)—thus in one example they give, wire 1 in the telephone lead is connected to wire 4 in the home extension wiring and wire 3 in the telephone lead is connected to wire 5 in the home extension wiring. In this way the VOIP signals are carried though the extension wiring over wires 4 and 5 and the DSL signals are carried through the extension wiring on (the normally used) wires 1 and 3 which are connected at the termination unit directly to the drop wire coming from the external access network. This approach, hereinafter referred to as a four wire solution, is a good solution where there is a spare pair of conductors reliably connected throughout a user's home extension wiring. However, in the four wire solution proposed in FR 2 933 835, the bell wire remains connected at the termination unit to the drop wires and so can still cause interference problems with the DSL signals carried onto the drop wires and over the data carrying conductors within the extension wiring. Furthermore, the approach would not work with telephony devices which require the presence of a bell signal on their incoming bell wire since the system makes no provision for such a bell signal to be generated.
Furthermore, in some situations there will not be such a spare pair of conductors reliably connected up through the extent of the user's home extension wiring (i.e. between the master socket and each extension socket). In many cases there may only be three wires reliably connected throughout the home extension wiring, namely the two normal data carrying wires and the third bell wire. In such a case, an alternative solution is required.